1. Technical Field
This disclosure relates generally to image forming apparatuses, electronic signature generating methods, electronic signature generating program products, and recording media, and more particularly to an image forming apparatus, an electronic signature generating method, an electronic signature generating program product, and a recording medium for attaching an electronic signature to image data read from a paper document.
2. Description of the Related Art
The e-document law (electronic document law) has been established, which allows scanning a paper document required by law to be stored, and to store electronic data of the paper document. To indicate that the scan data is authentic, it is required to attach an electronic signature of the operator or the field supervisor that scanned the document, to the scan data.
A method of addressing such a requirement has been devised. Specifically, when scanning a paper document with a scanner or a digital multifunction machine, the operator inserts his IC card into a card reader fixed to the scanner. An electronic signature key stored in the IC card is used to compute an electronic signature specific to each user. The electronic signature is attached to the scan data when the document is scanned. According to this method, an electronic signature of the operator or the field supervisor can be easily attached to scan data (see, for example, Japanese Patent No. 3616601, and Japanese Laid-Open Patent Application No. 2002-10044).
However, if by any chance the electronic signature key stored in the IC card is invalid (for example, a public key certificate corresponding to the electronic signature key has expired, or has been revoked for some reason), and it is realized that the electronic signature key is invalid after the scanning operation, the scanning operation needs to be done over again.
The same problem arises in the medical field with an apparatus for generating medical image data, such as a CT scanner. To indicate that image data was surely taken with a specific CT scanner by a specific radiological technician, the radiological technician inserts his IC card into the CT scanner. When the medical image data is generated, an electronic signature is attached to the image data by the IC card.